Edge and bevel cleaning process and system

ABSTRACT

The present invention provides at least one nozzle that sprays a rotating workpiece with an etchant at an edge thereof. The at least one nozzle is located in an upper chamber of a vertically configured processing subsystem that also includes mechanisms for plating, cleaning and drying in upper and lower chambers

This application claims the benefit of priority under 35 USC Section119(e) to U.S. Provisional Application Ser. No. 60/276,103 filed Mar.14, 2001, and is a continuation of U.S. patent application Ser. No.10/051,755 filed Jan. 15, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to semiconductor processingtechnologies and, more particularly, to a system and process thatremoves a conductive layer from the edge and/or bevel of a work piece.

2. Description of the Related Art

In the semiconductor industry, various processes can be used to depositand etch conductive materials on the wafers. Deposition techniquesinclude processes such as electrochemical deposition (ECD) and electrochemical mechanical deposition (ECMD). In both processes, a conductor isdeposited on a semiconductor wafer or a work piece by having electricalcurrent carried through an electrolyte that comes into contact with thesurface of the wafer (cathode). A detailed description of the ECMDmethod and apparatus can be found in U.S. Pat. No. 6,176,952 to Taliehentitled “Method and Apparatus For Electro Chemical MechanicalDeposition”, commonly owned by the assignee of the present invention.

Regardless of which process is used, the work piece is next transferredto a cleaning and drying station after the deposition step. During thecleaning steps, various residues generated by the deposition process arerinsed off the wafer, and subsequently the wafer is dried by spinningand if necessary blowing nitrogen on its surface. In one design, the ECDor ECMD chamber and the rinse chamber can be stacked vertically in avertical process chambers arrangement. In this arrangement, the platingprocess can be performed in a lower chamber, and the cleaning and dryingcan be carried out in an upper chamber after isolating the upper chamberfrom the lower chamber. One such vertical chamber is disclosed in theco-pending U.S. application Ser. No. 09/466,014, entitled “VerticallyConfigured Chamber Used for Multiple Processes”, filed Dec. 17, 1999,commonly owned by the assignee of the present invention.

Conventionally, after the plating process is performed to deposit theconductive material, the work piece may be polished mechanically andchemically, e.g., chemical mechanical polishing (CMP), so as to removeoverburden conductive material from the front face of the work piece. Asis known, the material removal can also be carried out using chemicaletching or electrochemical etching. In electrochemical etching, thewafer is made anodic (positive) with respect to an electrode aftercompleting an ECD or ECMD process.

Copper is a preferred conductive material that can be deposited by ECDand ECMD processes. Therefore it will be used as an example. As a resultof electroplating process, copper may be deposited on the edges andsides, i.e., bevel, of the wafer where no ICs or circuits are located.Such remaining copper, which is often referred to as the edge copper,may migrate to neighboring active regions from the sides and edges ofthe wafer. Further, copper from a wafer edge may contaminate the wafertransport system, and so be passed on to contaminate other wafers. Forthis reason, it is important to remove the copper from the edges and thebevel of the wafer following each copper plating process step.

To this end, there is a need for removing edge copper in copper platingprocesses in an efficient and effective manner with high throughput.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for removing an edge conductor that exists on a workpiece.

It is a further object of the present invention to provide a method andapparatus for removing an edge conductor in a vertically configuredchamber that also performs plating, cleaning and drying.

It is a further object of the invention to provide a method andapparatus for removing an edge conductor using a stream of etchantapplied to the edge of a workpiece.

The above object of the invention, among others, either singly or incombination, are achieved by the present invention by providing at leastone nozzle that sprays a rotating workpiece with an etchant at an edgethereof. The at least one nozzle is located in an upper chamber of avertically configured processing subsystem that also includes mechanismsfor plating, cleaning and drying in upper and lower chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objectives, features, and advantages of the presentinvention are further described in the detailed description whichfollows, with reference to the drawings by way of non-limiting exemplaryembodiments of the present invention, wherein like reference numeralsrepresent similar parts of the present invention throughout severalviews and wherein:

FIG. 1 illustrates a wafer on which edge removal is performed accordingto the present invention;

FIG. 2 illustrates a cross section of a wafer on which edge removal isperformed according to the present invention;

FIG. 3 illustrates a more detailed cross section of a portion of a waferon which edge removal is performed according to the present invention;

FIG. 4 illustrates a more detailed cross section of an edge portion of awafer on which edge removal is performed according to the presentinvention;

FIG. 5 illustrates a vertical chamber in which edge removal is performedaccording to the present invention;

FIGS. 6 and 7 illustrate the edge removal apparatus of the presentinvention in further detail; and

FIG. 8 illustrates an edge portion of a wafer that has had copperremoved therefrom according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a top plane view of a plated work piece 100 such as asemiconductor wafer. As also shown in FIG. 2 in side view, the platedwafer 100 comprises a top layer 102 having a top surface 103, a bottomlayer 104 having a bottom surface 105, a top surface edge 106 and awafer side 108 or bevel around the perimeter of the wafer surfaces 103and 105. In this embodiment, the top layer 102 of the plated wafer 100is comprised of a layer of electroplated conductive material, forexample copper, and the bottom layer 104 is comprised of a semiconductorsubstrate, such as a silicon substrate. In this embodiment copper iselectroplated on the substrate 104 using ECMD or ECD processes.

FIG. 3 is an enlarged partial cross-sectional view of near top surfaceregion 109 of the wafer 100, shown in FIG. 2, which comprises a via anda trench feature 110 and 112 formed in an insulating region 114 which ispreviously formed on the wafer surface. As shown in FIG. 3, the surfaceregion 109 of the plated wafer 100 may comprise a plurality of via,trench and other features such as dual damascene features. The features110, 112 and the surface of the insulator between the features may belined with a diffusion barrier/glue layer 116 and a seed layer 118,i.e., copper seed layer for the case of copper deposition. In mostcases, the barrier layer 116 and/or the seed layer 118 extends onto thetop surface edge 106, and sometimes onto the wafer side 108. In fact,one or both of these layers may wrap around and coat portions of thebottom surface 105 that is adjacent the wafer side 108. Since, duringthe electroplating, copper only deposits on the conductive regions thatare coated with barrier or copper seed layer or with a barrier/seedcomposite layer, this, in turn, causes copper to deposit on the edge106, the side 108 and the bottom surface 105. Electroplated copper layer102 fills the vias 110 and the trenches 112 and forms the interconnectstructure of the wafer 100, after the CMP process that removes theexcess copper and the barrier layer from the top surface of theinsulating region 114, therefore electrically isolating the copperregions within the various features. The interconnects are used toelectrically connect different active portions and levels in the chip orIC.

As mentioned above, the copper layer 102 may also extend onto the side108 and even the bottom surface 105 adjacent the edge 106, and thusforming an unwanted copper region 120 shown in FIG. 4. The edge copper120 may form around the circumference of the wafer 100. As exemplifiedin FIG. 4, the edge copper 120 may have an upper portion 122, a sideportion 124 and a lower portion 126. The edge copper portions 122-126can be removed from the top surface edge 106, side 108 and bottomsurface 105 by applying a copper etching solution through the process ofthe present invention. Although, in this embodiment, the edge copper isexemplified using the upper, side and lower portions, it is understoodthat this is for the purpose of exemplifying the problem; consequently,the unwanted copper may just have the upper portion.

It should be noted that even in the case where copper may not bedeposited in the regions 106, 108 and 105 of FIG. 4 during the platingstep, presence of the copper seed layer in those areas may exist and istypically undesirable. And a conventional CMP step carried out after theplating step may be able to remove any copper in the edge 106, but wouldnot be effective in removing copper from the side 108 and the bottomsurface 105.

The copper layer 102 may be deposited on wafer 100 using anelectroplating process and system 200 shown in FIG. 5. The system 200may be a vertical chamber comprising a lower section 202 and an uppersection 204. One such vertical chamber is disclosed in the co-pendingU.S. application Ser. No. 09/466,014, entitled “Vertically ConfiguredChamber Used for Multiple Processes”, filed Dec. 17, 1999, commonlyowned by the assignee of the present invention.

Accordingly, according to this embodiment, an edge copper removalprocess is performed within the upper chamber. Thus, while the lowerchamber will comprise some type of plating section, preferably comprisean ECMD process section but also a conventional ECD process section, theupper section will contain a cleaning and edge copper removal and dryingsection. The upper and lower sections have a movable barrier, describedin one specific embodiment as guard flaps, which keep the variousmaterials and solutions used in the processes of the upper chamber fromreaching the lower chamber, as described further herein. In oneembodiment of the process, an ECMD process is initially performed in thelower section 202, and in the following stage of the process, a cleaningby rinsing may be performed in the upper section 204. As will bedescribed more fully below, after the cleaning, in the upper section204, an edge copper removal process is performed. The edge copperremoval process is followed by a second cleaning and drying process.

A wafer holder 206 supports the wafer 100 as deposition process isperformed in the lower section 202. The wafer holder may comprise,preferably, circular chuck 207 upon which the wafer 100 is loaded,bottom surface 105 first (see FIG. 2), and secured. Guard flaps 208 vialinkage shafts/rollers 210 are positioned vertically such that the waferholder 206 using a shaft 212 can be lowered into the lower section 202.The shaft 212 is further adapted to move side to side and to rotateabout the vertical axis of the shaft 212. During the cleaning, edgecopper removal and drying, the wafer holder 206 is raised verticallyinto the upper section 204 and the flaps 208 are closed by moving themin the direction of the arrows 214.

During the ECMD process, as mentioned above, copper is applied in vias,trenches and/or other desired features in the wafer 100 (see also FIG.3) to form a generally flat copper layer over the features. An ECMDapparatus 215 may comprise a pad assembly 216 having a pad 217 placed onan anode 218 for depositing the copper on the wafer 100 while the wafer100 is polished. The copper can be applied using an electrolytesolution.

As shown in FIGS. 6 and 7, after the deposition takes place in the lowersection 202 of the system 200, the wafer holder 206 is raised using theshaft 212 to approximately its uppermost position. Then, the flaps 208are moved from their vertical position to their horizontal position toseparate the lower section 202 from the upper section 204. Once theflaps 208 are in closed position the cleaning is carried out. During thecleaning by rinsing, the holder 206 may be lowered towards the flaps208.

A conventional cleaning solution, depicted by the arrows 222, may beprovided through nozzles 224 which are located on the side walls 226 ofthe upper section and/or on the flaps 208. Used cleaning solution isdrained out of the section 204 using outlet channels 228 along the sidewalls 226. This solution does not mix with the electrolyte in the lowersection 202 due to the presence of the flaps 208 in the closed position.During the cleaning step, the wafer 100 is rotated and the cleaningsolution is applied to the wafer 100. The wafer 100 may be spun dried byrotating the wafer at high rpm. Additionally, clean and dry air or inertgas like nitrogen may also be blown on the wafer to help dry it. Afterthe cleaning and optionally drying processes, edge copper removalprocess is performed in the same upper chamber 204.

Referring to FIGS. 4, 6 and 7, during the edge copper removal, aconventional etching solution, depicted by the arrow 230, is applied onthe edge 106 of the wafer while the wafer 100 is rotated atapproximately 20 to 1000 rpm, preferably at 50 to 500 rpm. Etchingsolutions are typically acidic and oxidizing solutions which oxidizecopper and remove it at a high rate. Generally, the etching rate mayvary depending on the process time, temperature and the chemicalcomposition of the etching solution. The etchant is applied in the formof a well regulated stream through at least one nozzle 232 that ispreferably mounted on the flaps 208 or otherwise located relative to thewafer 100 such that the nozzle 232 directs a stream of the etchingsolution toward the wafer 100 in a manner that the stream has ahorizontal component that is directed away from the center of the wafer100, thus assisting with keeping the etching solution away from thecentral portion of the wafer and at the edge 106 of the wafer 100.

The etching solution can be fed to the nozzle 232 through a feed tube234 that is connected to a feed pump (not shown). The nozzle 232 directsthe solution to the edge 106 as a tightly controlled stream of etchingsolution. The etching solution can be applied in various amounts forvarious periods of time, preferably in a range of 1 to 10 ml per secondfor approximately 5 to 20 seconds. Owing to both centrifugal forcegenerated by the spinning wafer and the surface tension of the etchant,the etching solution arrives at the edge 106 at an angle and the streamof etchant that is outwardly directed to the upper portion 122 of theedge copper 120 flows over the portions 124 and 126 of the edge bead 120and covers them. The angle at which the etching solution strikes theedge 106 can also be varied, which allows for narrowing or broadening ofthe etched region. Etched region width can also be changed by moving thewafer and/or the nozzle laterally or vertically. If the nozzle isconstantly kept at a given angle, the etched region may be narrowed orbroadened by moving the wafer up and down or moving it laterally.Similarly if the wafer is kept in the same lateral position and sameelevation (but rotated), the etched region can be broadened or narrowedby varying the angle of the nozzle with respect to the wafer. As long asthe above given process works in the manner described, the nozzle may bepositioned on the walls or other places, and within the scope of theinvention. As shown in FIG. 8, accordingly, the etching solution etchesand removes the edge copper portions 122-126 from the edge 106, side 108and the bottom surface 105. In order to increase the etch rate, duringthe process, the etching solution or the wafer 206 or both may be heatedapproximately to a temperature less than 100° C., preferably 40-60° C.Heating of the etching solution or the wafer increases the etch rate andmay also assist the following drying step that follows rinsing step.After the etching process, the wafer is cleaned and dried.

Although various preferred embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications of the exemplary embodiment are possible withoutmaterially departing from the novel teachings and advantages of thisinvention.

1. A method of operating upon a surface of a workpiece, comprising:holding the workpiece with a workpiece carrier to expose the surface;forming a layer of conductive material on the surface while continuingto hold the workpiece with the workpiece carrier; and removing an edgeportion of the layer while continuing to hold the workpiece with theworkpiece carrier.
 2. (Canceled)
 3. The method of claim 1, wherein theremoving includes: rotating the workpiece; directing a stream of etchingsolution to a bevel edge and a front edge of the surface of theworkpiece; and removing the conductive material from the bevel edge andthe front edge of the surface.
 4. The method of claim 1, furtherincluding spraying a cleaning solution onto the layer prior to removing.5. The method of claim 4, further including rotating the workpiece todry the workpiece after spraying and prior to removing.
 6. The method ofclaim 1, wherein the forming includes an electrochemical mechanicaldeposition process.
 7. The method of claim 6, wherein the formingincludes an electrochemical deposition process
 8. The method of claim 3,further comprising heating the stream of etching solution.
 9. The methodof claim 3, further comprising rinsing and drying the layer afterremoving the conductive material from the bevel edge and the front edgeof the surface.
 10. The method of claim 1, wherein the conductivematerial is copper.
 11. An apparatus for operating upon a workpiecehaving a conductive layer on a front surface and a bevel edge of theworkpiece, comprising: a workpiece holder configured to hold theworkpiece and expose the conductive layer; a deposition chamberconfigured to operate on the conductive layer while the workpiece isheld by the workpiece holder; and an edge remover configured to removean edge portion of the conductive layer while the workpiece holdercontinues to hold the workpiece.
 12. The apparatus of claim 11, furtherincluding a workpiece cleaner configured to clean the workpiece afterthe deposition.
 13. The apparatus of claim 11, wherein the edge removerincludes at least one edge conductor removal device configured to supplya stream of an etching solution toward at least the edge of theworkpiece.
 14. The apparatus of claim 13, wherein the at least one edgeconductor removal device comprises at least one nozzle disposed within aposition relative to the workpiece such that the stream of the etchingsolution is directed outwardly toward the edge of the workpiece.
 15. Theapparatus according to claim 14, wherein the at least one nozzle isdisposed to direct a cleaning solution towards the front surface of theworkpiece.
 16. The apparatus of claim 11, wherein the conductive layercomprises copper.
 17. The apparatus of claim 11, wherein the depositionchamber is configured for electrochemical deposition.
 18. The apparatusof claim 11, wherein the deposition chamber is configured forelectrochemical mechanical deposition.